Two NASA probes have discovered a previously unknown ring of radiation blanketing the Earth, upending a long-standing scientific theory about how charged particles coalesce around the planet, scientists reported last week.

Just four days after the twin Radiation Belt Storm Probes were launched in August, NASA scientists looked on in amazement as instruments revealed a third belt of high-energy particles between the planet's inner and outer radiation belts, known as the Van Allen belts.

The new belt held steady for four weeks before a solar flare blasted it to pieces. It has not been seen since.

The twin probes were the first built by NASA to study the radiation belts, which were discovered in 1958 by astrophysicist James Van Allen. The inner belt is between 6,000 and 8,000 miles out and the outer belt forms at about 15,000 miles.

Scientists have found charged particles hovering between the inner and outer belts before, in 1991 and 1992. But they were never this stable or remained as long as a month.

"There are a host of different processes that occur in radiation belts," Fox said. "What we do not yet know is why sometimes one is more dominant than another. It is like knowing all the ingredients but not the proportions."

The so-called Van Allen probes gave scientists their best glimpse yet at those proportions. Equipped with identical particle, plasma, magnetic field and plasma wave sensors, the probes measured charged particles in and around the planet's magnetosphere between September and October.